1. Field of the Invention
This invention relates generally to the field of fasteners, and in particular to those washer type devices which incorporate anchoring legs to prevent rotation of the device in the workpiece. This invention combines the above anti-rotation features with an axial-loaded lock washer function.
2. Description of Related Art
Many types of special fasteners exist in the prior art. An example of these is described in U.S. Pat. No. 3,304,830 by Shackelford for an Expansible Hollow Rivet Having A Polygonal Shank. In U.S. Pat. No. 3,550,217, Collyer describes an invention that relates to a plastics fastener for attachment to an apertured workpiece and comprises a head for abutment against the outer surface of the workpiece and a shank for a snap-engagement through the aperture.
Another class of frequently used types is the internally threaded fastener. These conventional threaded insert devices are placed in a hole in the workpiece, which is generally thin gauge metal sheet or metal plate stock and then, with the use of a special tool, are collapsed. Structural components may then be mounted to the workpiece by means of a bolt or screw in conjunction with the threaded insert. Exemplary fasteners of this type are found in U.S. Pat. Nos. 3,304,830 and 3,750,525.
In U.S. Pat. No. 3,750,525, Waters et al. shows an improved collapsible threaded insert device for securing items to a plate-like workpiece of the type consisting of an annular flange portion integrally attached to an internally threaded, collapsible shank portion. The improvement comprises the addition of various mechanical gripping means formed on the undersurface of the flange to frictionally engage the workpiece when the threaded insert device has been collapsibly secured thereto, thus, increasing the resistance to rotation of said insert within the workpiece.
More recent designs include U.S. Pat. No. 5,118,235 to Dill for a washer molded from a polymeric material and useful with a fastener having a head and shank, such as, for example, a screw or a drive pin, and a fastening assembly comprised of the washer and such a fastener, is a disclosed. The fastener head is contained within a washer socket with the fastener shank extending through a washer aperture. An integral flap hinged from a lateral wall portion of the washer socket is used to substantially cover the fastener head.
Other designs include U.S. Pat. No. 3,903,573 to Wilson for "Arcuate, stamp down fasteners for sheet securement." Rapata's U.S. Pat. No. 2,836,215 for "Plastic Nut-Like Fastener with Resilient Wings;" O'Conner's U.S. Pat. No. 3,384,938 for "Pliable Material Clamp;" Schuplin's U.S. Pat. No. 3,417,438 for a "Deformable Polymeric Fastening Device;" Heidelberger's U.S. Pat. No. 3,609,822 for a "Fastening Device;" and Bowerman's U.S. Pat. No. 3,686,616 for a "Fastener."
None of the above provide both rotational and axial restraint with the simplicity of this invention.